I enjoyed this game quite a bit! The art and sound style are really appealing, and the overall aesthetic of the game is great!
My main criticism for this game is in the controls. Personally, I'm not a huge fan of having the character jump if the space bar is held down. The reason I feel this way is because the character jumps higher when the space bar is held down, so often times I'll still be holding the space bar after a jump and when the character lands, they end up jumping again even though I did not intend to do that.
The other issue I had with the controls is that the rocket jumping, although a really AWESOME concept, was pretty hard to control. It's hard to describe, but it felt as though an additional force was being applied to the character after a rocket jump that made him move in unexpected ways. This made precision jumping sections extremely difficult.
I did end up completing the game, though I did not collect all the stars unfortunately :(. Aside from those issues with the controls, I think your entry was super good!